Group A streptococci (GAS) are responsible for a wide variety of diseases. These range from uncomplicated pharyngitis to more serious invasive diseases such as necrotizing fasciitis (“flesh eating syndrome”) and streptococcal toxic shock syndrome. Additionally, approximately 3% of GAS infections that go untreated will result in acute rheumatic fever. (Brandt, E. R., Good, M. F. 1999. Vaccine strategies to prevent rheumatic fever. Immunol. Res. 19:89-103) All ages are susceptible to GAS attack, but those particularly vulnerable are the elderly, children under 2 years, and African Americans. (Emerging Infections Programs (EIP), supported by the National Center for Infectious Diseases for isolates resulting from active surveillance 1995-1997. California EIP: Arthur Reingold; Connecticut EIP: Matt Carter; Georgia EIP, Monica Farley; Minnesota EIP, Kristine MacDonald; Oregon EIP, Paul Cieslak; Centers for Disease Control and Prevention (CDC), K. O'Brien, B. Beall, K. Deaver-Robinson, R. Facklam, A. Kraus, A. Schuchat, B. Schwartz) Recently, there has been a significant increase in the number of streptococcal infections (Davies, H. D., McGeer, A., Schwartz, B., et al. 1996. Invasive group A streptococcal infections in Ontario, Canada. Ontario group A streptococcal study group. N. Engl. J. Med. 335:547-54) as well as rheumatic fever (Veasey, L. G., Wiedneier, S. W., Osmond, G. S., et al. Resurgence of acute rheumatic fever in the intermountain region of the United States. N. Engl. J. Med. 316:42-7). Based on recent active surveillance, it is estimated that there are approximately 8,500 cases and 1,300 deaths annually in the United States from invasive GAS disease, (EIP supported by the National Center for Infectious Diseases for isolates resulting from active surveillance 1995-1997. California EIP: Arthur Reingold; Connecticut EIP: Matt Carter; Georgia EIP, Monica Farley; Minnesota EIP, Kristine MacDonald; Oregon EIP, Paul Cieslak; CDC, K. O'Brien, B. Beall, K. Deaver-Robinson, R. Facklam, A. Kraus, A. Schuchat, B. Schwartz).
A vaccine against GAS could eliminate millions of dollars in health care costs and numerous physician visits.
There are a number of strategies that have been used towards designing an effective streptococcal vaccine (Salvadori, L. G., Blake, M. S., McCarty, M., Tai, J. Y., Zabriskie, J. B. 1995. Group A streptococcus-liposome ELISA antibody titers to group A polysaccharide and opsonophagocytic capabilities of the antibodies. J. Infect Dis. 171:593-600; Ji, Y. Carlson, B., Kondagunta, A., Cleary, P. P. 1997. Intranasal immunization with C5a peptidase prevents nasopharyngeal colonization of mice by group A streptococcus. Infect Immun. 65:2080-2087; Kapur, V. Maffei, J. T., Greer R. S., Li, L. L., Adams, G. J., Musser, J. M. 1994. Vaccination with streptococcal cysteine protease protects mice against challenge with heterologous group A streptococci. Microb. Pathogenesis. 16:443-450; Dale, J. B., Baird, R. W., Courtney, H. S., Hasty, D. L., Bronze, M. S. 1994. Passive protection of mice against group A streptococcal pharyngeal infection by lipoteichoic acid. J. Infect. Dis. 169:319-323; Dale, J. B., Washburn, R. G., Marques, M. B., Wessels, M. R. 1996. Hyuaronated capsule and surface M protein in resistance to opsonization of group A streptococci. Infect Immun. 64:1495-1501; Fischetti, V. A. 1989. Streptococcal M protein: molecular design and biological behavior. Clin. Microbiol. 2:285-314; Lancefield, R. C. 1962. Current knowledge of the type-specific M antigens of group A streptococci. J. Immun. 89:307-313; Lancefield, R. C. 1959. Persistence of type-specific antibodies in man following infection with group A streptococci. J. Exp. Med. 110:271-283).
There are difficulties associated with a vaccine strategy involving the M protein, such as the large number of serologic M (emm) types (over 100 serotypes) and the observation that some M proteins contain epitopes that cross-react with human tissues. In addition to the large number of serotypes, every population has a different subset of GAS serotypes which are the most prevalent. In order to deal with these difficulties, different approaches have been tried. For example, observation that the M protein's C-terminus is conserved while the N-terminus is variable has led some workers to try to focus on the C-terminus for broader protection and others to focus on the N-terminus where the most variability is.
Even though some M protein-based vaccines have been designed, for the above reasons, a need still exists for a flexible, effective, multivalent GAS vaccine.